Structure of MgSO_4 in Concentrated Aqueous Solutions by X-Ray Diffraction

Detailed time-and-space-averaged structure of MgSO4 in the concentrated aqueous solutions was investigated via X-ray diffraction with an X’pert Pro θ-θ diffractometer at 298 K, yielding structural function and radial distribution function(RDF). The developed KURVLR program was employed for the theoretical investigation in consideration of the ionic hydration and ion association. Multi-peaks Gaussian fitting method was applied to deconvolving the overlapping bands of Differential radial distribution function...     

Effect of Oxygen Environment on the Decomposition and Crystallization of an Aqueous Sol-Gel Derived Zirconium Acetate Gel

A precursor gel was prepared by desiccation of an aqueous solution of zirconium acetate and pyrolyzed to form crystalline powders in selected gas environments. Thermal analysis, X-ray powder diffraction, mass spectrometry and Fourier transform infrared spectroscopy were used to investigate the decomposition of the gel and the transformations occurring during pyrolysis to 800°C in nitrogen, air and oxygen. Three transition temperatures were detected: the amorphous-to-cubic crystal transformation, cubic-to-tetragonal transformation, and the initiation of tetragonal-to-monoclinic transition. The presence of molecular oxygen decreased the crystallization temperature, increased the grain size of the tetragonal crystals formed and decreased the temperature at which the tetragonal-to-monoclinic transformation was initiated. The decrease in the crystallization temperature in the presence of oxygen occurred despite an increase in the temperature corresponding to the loss of the major portion of the organic component of the gel.     

X-Ray Diffraction Study of Some Liquid Naphthalene Derivatives

Abstract

The structure of the liquids 1-Methylnaphthalene C₁₀H₇—CH₃ and 1-Chloronaphthalene C₁₀H₇—Cl was investigated using X-ray diffraction at 293 K. Monochromatic radiation MoK_α (λ = 0.7107Å) enabled determination of the scattered radiation inteasity between S₀ = 4pi sin υ₀/λ = 0.430 Å^?1 and S _max = 14.311 Å-1. Angular distributions of X-ray scattered intensity were measured, and differential radial distribution functions of electron density (DRDFs) were calculated. The mean distances between the neighbouring molecules and the ranges of the spheres of intermolecular ordering were found. X-ray structural analysis was applied for determination of the packing coefficient of molecules of the liquids studied. A simple model of short-range arrangement of the molecules was proposed, which seems to be valid for other weakly polar monosubstituted naphthalene derivatives in the liquid phase.     

无机聚合絮凝剂的结构研究

本文用广角度Ｘ射线散射（ＷＡＸＳ）和径向分布函数（ＲＤＦ）方法对聚合硅硫酸铝钾ＴＸ２０３絮凝剂的结构进行了分析。ＷＡＸＳ和ＲＤＦ分析指出：该絮凝剂是一种有序尺寸（Ｄ）约为２２～２５Ａ非晶固体。它是由有序周期（ｒ、）≌１２－１４Ａ的中程有序畴组成的,而这些有序畴又是由三种结构单元,即四面体「ＳＯ４」,「ＡｌＯ４」（０＝Ｏ,ＯＨ）和八面体「ＡｌＯ６」（Ｏ＝Ｏ,ＯＨ）组成的。Ｄ／ｒ１＝２～３,因此ＴＸ２     

Chemical Behaviour of Zirconium Oxychloride Octahydrate and Acetic Acid in Precursor Solution for Zirconia Film Formation on Glass

Precursor solutions for zirconia films on soda lime silica glass substrate were prepared from zirconium oxychloride octahydrate (ZOO) and acetic acid (HOAC) maintaining the mol ratios, [HOAC]/[ZOO] = 2, 4, 6, 8 and 10. A characteristic UV absorption band at ～280 nm in the ～120 h aged precursor solutions was identified for acetate group of the zirconium acetato complexed species. The presence of acetate ligand coordinated with either ZrOOH+ or [Zr4(OH)8]8+ or with both was predicted by the studies of UV spectra of aged solutions and FTIR spectra of unbaked films on silicon wafer. Dipping technique was followed for film formation. Thicknesses and refractive indices of the baked (450° ± 5°C) films were in the ranges 1818 ± 20 Å and 1.702–1.762 respectively. The positive SIMS experiment on two typical films baked at 450° ± 5°C derived from the precursors with [HOAC]/[ZOO] = 2 and 6, detected the ionic species, Zr+, ZrO+, ZrO2+, Na+, Ca+, Fe+, H+ while the negative SIMS detected O- and Cl-. The relative contents of the ionic species with respect to Zr+ were dependent on the acid content of the precursors. Reflection (%) of the baked films in the UV region was also dependent on the acid content of the precursors. Electron diffraction pattern of the typical baked film derived from the precursor with [HOAC]/[ZOO] = 2 exhibited meta-stable cubic phase of zirconia and the grains were found to be elongated (aspect ratio, 2.00–2.33).     

Structural Features of Phosphate and Sulfate Modified Zirconia Prepared by Sol–Gel Route

This paper describes the effect of sulfate, phosphate and nitrate complexing ligands on the structural features of amorphous xerogels and on the crystallization of metastable zirconia phases during the xerogel-ceramic conversion. Powdered samples were prepared by a sol–gel route using zirconyl chloride precursors chemically modified by complexing ligands. The structural evolution of ZrO₂ phases as function of firing temperature was analyzed by XRPD, EXAFS and ³¹P NMR/MAS. The experimental results show the formation of metastable t-ZrO₂ during the low firing temperature of xerogels modified by sulfate or phosphate groups. The martensitic tetragonal-monoclinic transformation occurs during desorption of sulfate groups. The largest temperature interval of stability of metastable tetragonal zirconia was observed for phosphate-modified xerogels.     

温度对液态水结构的影响：中子及X射线散射研究

采用中子散射和X射线散射研究了液态水在298～373 K温度范围内的结构,通过偏径向分布函数(PDF)、配位数分布(CN)、角分布(ADF)及空间密度分布(SDF)等讨论了温度对液态水结构的影响。整体来看,液态水具有"不规则四面体"氢键网络的短程有序结构,该有序度可延续到第三水合层。液态水分子的第一水合层中,围绕中心水分子约有4.8个水分子,然而其中仅有约3.3个水分子与中心水分子通过氢键相键合,约1/3进入到第一水合层的水分子并未与中心水分子直接键合,也正是这些间隙水分子的存在加剧了液态水结构的复杂性。温度对液态水的有序度存在一定的影响,在298～373 K的有限温度变化范围内,温度对液态水中氢键的键长、键角分布及第一水合层SDF的影响不大。从298K升温到373K,O(W)-O(W)距离仅增加0.03?,氢键数目也仅有微小减少,温度对第二和第三水合层的影响则要显著很多。     

三氧化二硼和五硼酸钠水合物非晶结构

X射线衍射法测量了三氧化二硼及五硼酸钠水合物的非晶结构, 通过非晶衍射实验数据处理, 得到了它们的径向分布函数(RDF). 模型定量计算, 得到了其短程有序结构, 三氧化二硼水合物非晶中75%的硼参与形成平面硼氧六元环(boroxol), 给出了环内ortho-B-O, meta-O-O, meta-B-B和para-B-O相互作用的距离和作用数, 支链与硼氧六元环之间的夹角为125°±15°; 五硼酸钠水合物非晶中, 由两个硼氧三角形(B_△)和一个硼氧四面体(B_□)构成的两个变形六元环通过公共顶点(B_□)相连而形成五硼酸阴离子, 高度有序的离子内相互作用占绝对优势. 六配位Na^＋与五硼酸阴离子中一端氧相连, Na-B特征距离为0.330 nm.     

锂-,钠-,钾水化蒙脱石层间结构的分子动力学模拟

运用分子动力学(molecular dynamics, MD)方法分别研究了含有32, 64和96个水分子的Li-, Na-, K-蒙脱石层间阳离子与水分子的位置和结构. 计算结果表明蒙脱石层间阳离子位置与四面体和八面体电荷位置及离子的大小有关. 一层水合物中可以观察到三种阳离子都能和四面体电荷与八面体电荷位置分别形成内、外配位作用. 二层水合物中, 仍然可以观察到Li^＋和Na^＋与电荷位置的配位作用, 但是已经开始向层中其他方向扩散, 而K^＋仍然在粘土的表面附近. 三层水合物中, Li^＋, Na^＋开始从电荷位置和表面分离, K^＋也开始向层间其他方向扩散. 水分子在所有三种水合物中都分散于层间各个方向. 径向分布函数的分析结果表明层间三种阳离子组织水分子的能力不同, 水化作用随着阳离子半径的增大而减弱; 此外层中水分子的聚合程度随着水分子的增加而加强, 水分子的结构也不同于模拟的液体水分子的结构; 说明蒙脱石层间阳离子的溶剂化作用对水分子的组织起着重要的作用.     

ChemInform Abstract: Structure of KNaReH9 by Single Crystal X-Ray Diffraction and Infrared Spectroscopy.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Quantitative EPMA of element depth distribution

A new model for the ionization depth distribution function has been proposed. Within the framework of this model full electron flux is considered to be divided into two fluxes propagating in forward and backward directions through a sample. The intensities of these fluxes can be derived on the basis of simple assumptions of electron-solid interactions. The approach can be effectively applied to a system with an arbitrary form of depth concentration profile. The obtained results are in reasonable agreement with Monte Carlo simulations and experimental results. Some mathematical techniques have been presented for quantitative analysis of thin films on substrates and element depth distribution.     

Characterization of Tin Oxide Based Sol-Gel Coatings on Borosilicate Glasses by X-Ray Reflectivity

The X-ray reflectivity technique was applied in the study of tin oxide films deposited by sol-gel dip-coating on borosilicate glasses. The influence of the withdrawal speed and temperature of thermal treatment on the film structure was analyzed. We have compared the thermal evolution of the density and the shrinkage of the films with these properties measured for the monolithic xerogel by helium picnometry and thermomechanical analysis. In agreement with the Landau-Levich model, the layer thickness increases by increasing the withdrawal speed. Nevertheless, it decreases with the increase of the thermal treatment temperature, due to the densification process. The values of apparent density are smaller than the skeletal density, which shows that the films are porous. The comparison between the film and the monolith indicates that shrinkage during firing is anisotropic, occurring essentially perpendicular to the coating surface.     

Approach on Tsallis statistical interpretation of hydrogen-atom by adopting the generalized radial distribution function

This paper revisits the statistical interpretation of the hydrogen atom within the framework of Tsallis Statistical Mechanics in the Canonical Ensemble. The convergence of the partition function does not exhibit for all the temperatures, while the well-known T → T′ transformation method of Tsallis Statistics fails, since non-monotonicity is observed between the ordinary temperature, T, and the auxiliary one, T′. Here we re-examine the inconsistency of T → T′ transformation method, in the case where the partition function converges for all the temperatures, by considering the generalized radial distribution function. We find that both the transformation method inconsistency and the partition function divergence can be recovered for all the temperatures, if the hydrogen atom is restricted within a critical radius R _c  ≤ 4.832 bohr, while Tsallis entropic index values are given by . An erratum to this article can be found at     

溶胶-凝胶法制备金属铂高分散的二氧化钛薄膜

Uniform and crack free TiO 2 thin films with highly dispersed platinum were prepared from i PrOH TTIP DEA H 2O system containing H 2PtCl 6·6H 2O as metal source by sol gel method. The microstructure and morphology of the films were characterized by TEM and XRD respectively. It was found that the Pt particles dispersed in the films and had a homogeneous distribution in the shape of sphere with an average size of about 5 nm. This study also showed that the doping with few percent of Pt resulted in the formation of pure rutile phase at a temperature as low as 550 ℃, whereas the same pure phase was formed at the temperature higher than 650 ℃ in TiO 2 or Au/TiO 2 thin films.     

The role of thermal analysis in optimization of the electrochromic effect of nickel oxide thin films, prepared by the sol–gel method: Part II

Thin films and the corresponding xerogels were prepared from nickel acetate precursor using the sol–gel dip-coating technique. The differences in thermal stability of the two forms of samples were studied by dynamic and isothermal thermogravimetry. For thin films, the onset decomposition temperature of acetate groups was 230 °C and for the xerogel 250 °C. During thermal decomposition, the formation of nanosized nickel oxide took place. Carbonate ions, which were formed during thermal decompostion of acetate groups, remained either free or bidentately coordinated to nickel. In situ monochromatic optical transmittance changes showed that an optical stability up to the 100th cycle was already achieved for films heated for 15 min at the isothermal temperature (thermal decompositon 25%). Comparison of the results obtained for nickel sulfate (Part I) and nickel acetate precursors shows that at least two parameters, the precursor used and the degree of thermal treatment, have considerable influence on the thermal stability of the thin film and also on its electrochromic response during the cycling process.     

水化锂蒙脱石层间结构和动力特征的分子模拟

利用分子力场和分子动力学(MD)的方法研究了Li-蒙脱石的结构构型, 层间阳离子的水化行为、水分子的结构特征以及它们的扩散性质. 分子力场构型优化结果表明: Li-蒙脱石的层间距、体积和密度与层间水含量有关; MD模拟的动画轨迹显示Li-蒙脱石层间Li^＋的位置与层间电荷位置有关. 均方根位移和自扩散系数的计算结果表明: 层间阳离子、水分子在Li-蒙脱石一、二层水合物中的扩散受到上下粘土片表面的限制, 在三层水合物中开始离开粘土层面向其它方向快速扩散. 径向分布函数及其结构因子的分析结果表明Li^＋在一、二、三层水合物中有不同的水合层; 层间水分子的结构特征说明其在蒙脱石层间有水合水分子和自由水分子之分, 且它们的比值在一、二和三层水合物中有所不同.     

均相与非均相法合成的纤维素乙酸酯结构与性能的比较研究

研究了离子液体中均相反应制备纤维素乙酸酯(CA_(Homo))与非均相反应制备纤维素乙酸酯(CA_(Hete))的化学结构,进而比较了化学结构差别对纤维素乙酸酯性能的影响.均相与非均相法制备的CA化学结构存在显著差异,CA_(Homo)相比CA_(Hete)具有更好的均匀性,且CA_(Homo)和CA_(Hete)的取代基分布不同,CA_(Homo)的乙酰基取代顺序为C-6C-3C-2,CA_(Hete)的乙酰基取代顺序为C-3C-2C-6.同时对CA_(Homo)和CA_(Hete)的结晶行为、溶解性和热性能进行研究,结果表明,不同化学结构对CA的这些宏观性能影响较小,CA_(Homo)和CA_(Hete)均为无定型结构,可溶解于极性有机溶剂中,玻璃化转变温度和热稳定性相近.因此,通过离子液体均相制备的CA与现有非均相法制备的CA具有相似的物理性能,但均相法制备的CA结构均匀性更好.